Buoy marine lanterns serve, for example, as navigational aids to provide rugged markers for underwater obstructions and navigational channels. When properly moored, the buoys with lantern will withstand hurricane force winds and seas.
The present lantern employs a gimbal whose main purpose is to compensate for the list of the buoy caused by wind and current. An objection to the use of gimbals for marine lanterns is the resultant violent motion thereof when the period of the buoy oscillation coincides with the natural frequency of the gimbal mechanism. Very often, the gimbal is destroyed as well as damage being suffered by the lampchanger and flasher.
The present gimbal eliminates any possibility of violent motion thereof. It is appreciated that the effects of the list of the buoy caused by the wind and current occur rather slowly. The present gimbal is caused to respond slowly to these effects by means of a very viscous fluid in the lantern body which immerses the counterweights suspended from the gimbal, and the use of plastic hinges for the gimbal in lieu of conventional bearing members.
The heavy dampening provided by the viscous fluid and plastic hinges result in a gimbal having a very long natural period of vibration, thus minimizing the harmful effects caused by the wind and current. Rapid response is not needed because the present lantern compensates principally for the list of the buoy, and not for rapid wave motion of small waves. The gimbal will respond however, to a degree, to all motions, so performance will be improved even for wave motion.
The present gimbal includes an outer frame, preferably square or rectangular in cross-section, and an inner member mounted thereto by means of a pair of hinges articulating therebetween, and another pair of hinges articulating between the outer frame and housing of the lantern, each pair of hinges being disposed along different axes.
The inner gimbal member or frame suspends the counterweights therebelow which are immersed in a dampening liquid medium having a viscosity of approximately 100,000 SSU. Supported on the inner gimbal member are the drum lens, lampchanger and flasher.
Due principally to the present gimbal structure, the buoy lantern remains in a substantially vertical position for angles of inclination of the buoy about .+-.9.degree., or a total of 18 degrees. As a result, the effectiveness of the buoy light is improved. That is, a lamp of considerably lesser wattage may be used in the present lantern to obtain an equivalent range of a lantern without the improved gimbal at appreciable angles of list of the buoy.